The invention is based on the priority application EP 06301157.1 which is hereby incorporated by reference.
The present invention relates to indoor communications systems, and particularly to wireless cellular communications systems in buildings and tunnels.
Wireless communications systems are becoming an increasingly widespread phenomenon of modern communications. Since many users place an increasing number of cellular calls or data transmissions within buildings or other confined structures, there is a need to achieve high quality indoor coverage at appropriate capacity.
A conventional configuration to extend a wireless communications service e.g. GSM or UMTS, from an outdoor environment to an indoor area is shown in FIG. 1 and is characterized by the utilization of a repeater R that is typically located within a building B to retransmit within the building a wireless signal Ws received at an external antenna A1 or retransmit outside the building the wireless signals Ws of mobile stations Ms, e.g. mobile phones, handheld computers and the like, located inside the building B. In the downlink, that is when the wireless signals Ws from the external environment are transmitted to the mobile stations Ms inside the building B, said outdoor wireless signals are passed along a first connection Co1 to the repeater R which forwards the signal along a second connection Co2 to a plurality of inter-connected amplifiers Am, the amplifiers amplify the signals which are then transmitted over the in-building antennas A2 to A4. In the uplink direction, that is, when the wireless signals Ws from the mobile stations Ms are transmitted to a wireless infrastructure outside the building B, the repeater R receives said signals along connection Co2 and transmits them along connection Co1 to the external antenna A1.
It is also possible that the repeater R of the indoor communications structure is replaced by a base station connected to a communications core network along connection Co1. Typically, the information is distributed via analogue signals inside the buildings and confined areas.
Another known indoor communications system providing wireless cellular service is shown in FIG. 2. A core network CN is connected to a base station Bs. The radio frequency (RF) signals from the base station or an off-air repeater OAR are digitized into base band signals in a base station interface BSI (and vice versa in uplink transmission) and distributed in the form of data packets using data cables, e.g. category 5 (CAT5) or optical fiber, to at least one Ethernet switch ES. The Ethernet switch ES then distributes the information to the corresponding remote radio heads RH1 to RH4 serving a particular cell area C1 and C2. An example of such system is disclosed in Patent Application US 2005/0157675 A1. An advantage of such systems is that they provide a cost-effective solution due to the use or re-use of low cost distribution cabling which is usually already present, totally or partly, in buildings and used for other types of digital communications e.g. local area network LAN structures using Ethernet protocol.
Using standard Ethernet switches, cell configurations can be achieved due to the sectorization of data flow. Normally, an Ethernet hub is needed in each Ethernet sector for data distribution in downlink and data packaging in uplink. The hub function is placed in at least one of the associated remote radio heads. In complex systems, series of Ethernet switches are necessary and bottlenecks of data flow are evident due to the 1 to n distribution characteristic of the Ethernet switch resulting in limiting the capacity of the network.